1. Field of the Invention
The present invention relates generally to photonic sensors, and more particularly to electro-optic antennas and sensors for wideband reception and processing of electromagnetic signals.
2. Related Art
Array antennas for reception and transmission of electromagnetic signals are well known in the art. One important objective in the refinement of this type of antenna is to increase the operational bandwidth of the antenna.
Traditional arrays use conventional antenna elements. One disadvantage of this type of element is that it is usually limited to a small operational bandwidth. Further, these elements require some sort of transmission line, such as coaxial cable, microstrip, or stripline, to connect to each antenna element and a feed network. For antenna arrays having many elements, this approach results in structures that are quite heavy and large. Another disadvantage that results from this approach is an increase in backplane complexity. A further disadvantage is the substantial signal losses that are incurred on the transmission lines, as the desired frequency of operation is increased.
One conventional approach to increasing bandwidth is to use a "spiral" antenna element within the array. One disadvantage of this approach is that such spiral elements become large as the frequency of operation is reduced. Further, the spacing of these elements increases, resulting in a physically large structure. Further, this large spacing has adverse effects on the operation of the array. A further disadvantage is the backplane complexity mentioned above.
Another conventional approach is to use electrically small antennas to get around the spacing issue. However, the efficiency of this class of antennas is usually very poor.